Hi. I working on a friends jdm s5 t2 and did the rats nest delete. It had a lot of vacuum leaks espcially from the injector seals on primary injectors. When he borught it it also had a high idle and would bog when trying to hit boost on the dyno and on street. I fixed the leaks and put it back together. When i start it. It now idles too low and when i try to hold the throttle to keep it from dying it starts to idle like it has a bridgeport. Its running on an Apexi Power FC. I double checked everything and its all sealed. it breaks up a bit too when reving it slowly up the rpms. but if i blimp the throttle up fast it seems to rev normal. Would anyone have any ideas or have had this issue? The BAC is still connected.

 

First things first. What was the objective with the vacuum system delete? Are you making a race car?

If you are wanting a street car, you will want to keep many features of the stock vacuum system. An emissions delete is one thing, but eliminating the whole system without a suitable replacement will cause drivability to suffer. The vacuum system is not only responsible for the fuel pressure regulator, but the air bleeds provide the air required for engine idle. Often times, guys will pull out the vacuum system and think that the problem is throttle related. They will then adjust the throttle body for idle adjustment (not what its for, idle adjust is on the BAC), and then the TPS are out from where they should be.

In addition, did you get rid of the coolant lines running to the throttle body? Also, did you do a compressed air test in the intake to check for leaks?

If you want to put the vacuum system back in, we can help you get it back together. I've been recording some videos on how the stock vacuum system works, and how to reset it all if it's been monkeyed with. Now that it's warming up, I've got just one or two to do and then I can post them.

 

Sounds tune related with cold start settings. assuming you’ve already adjusted tps, and idle adjustment on the throttle body. You mentioned a power fc but never said it was tuned. I’m running a power fc with a base map I modified from banzai racing and my car did the same thing yours is doing, then it would idle perfectly fine right when it hit 150 degrees Fahrenheit.

 

figured it out. the map sensor wasnt reading anything and the tps was out of adjustment. It mightve moved when i took took off the throttle body to clean it. idles smooth now.